PEORIA, Ariz. -- With just over a week left until the Mariners have to set their 25-man roster for Opening Day, five questions remain to be decided. Here's a look at the decisions facing general manager Jerry Dipoto, manager Scott Servais and their staffs:

The fifth starterNathan Karns and James Paxton came to camp in a toss-up situation for the final rotation berth and that still appears to be a tough call as neither has had a great spring.

Paxton starts Sunday against the Cubs in Mesa, with Karns going Monday against the Royals in Peoria. It might come down to those starts in determining who opens the season with the club, but it's worth remembering that it's a long season and whoever doesn't open the year with the Mariners could be quickly recalled from Triple-A Tacoma if problems arise with any of Seattle's starters.

Paxton's nice outing

LAD@SEA: Paxton goes four innings, strikes out two

3/12/16: James Paxton pitches four innings, striking out two batters and allowing one run

Backup catcher
Left-handed hitters Steve Clevenger and Rob Brantly are also involved in a close battle behind starter Chris Iannetta. Clevenger, acquired from the Orioles for Mark Trumbo, seemed the clear choice at the start of camp, since the plan has been to let Mike Zunino spend time in Tacoma to gain confidence and at-bats. But Brantly was claimed off waivers from the White Sox two weeks ago and has hit well enough to make it interesting.

Both players are out of Minor League options, so that makes this one tougher as the loser could well be claimed by another club. Clevenger seemingly remains a slight favorite since he's been with the team all spring and has been better defensively than expected, but Brantly is three years younger at 26 and his upside is intriguing.

Clevenger's RBI single

SEA@COL: Clevenger plates Smith with a single

3/24/16: Steve Clevenger grounds an RBI single to center field, scoring Seth Smith to extend the Mariners' lead

"I'm very comfortable with either one of those guys," Servais said. "Obviously, I have a little longer track record with Clevenger, having been with him from the start of camp. But Brantly brings some different things offensively as well, so I think we're in a good spot there. Catching is hard to find and there's a lot of clubs looking for it."

Brantly's RBI single

SEA@COL: Brantly grounds an RBI single to right

3/24/16: Rob Brantly grounds a single to right field, scoring Austin Wilson in the top of the 8th inning

Backup first baseman
It'll be decision time shortly with Korean slugger Dae-Ho Lee, who has a Sunday opt-out date in his Minor League contract. The Mariners either need to put Lee on their 40-man roster or risk having him go elsewhere, but they also have to decide if the big 33-year-old's skillset fits their needs as a right-handed complement to starter Adam Lind.

Lee's RBI single

SEA@LAA: Lee opens scoring with RBI single to left

3/15/16: Dae-Ho Lee lofts an RBI single to left field, driving in Stefen Romero to give the Mariners an early 1-0 lead

Outfielder Stefen Romero has presented a strong alternative as the 27-year-old hit extremely well early in spring and is more athletic and versatile than either Lee or Jesus Montero, the other candidate. Montero is out of Minor League options and hasn't hit as well as hoped this spring. Romero might be viewed as the best choice at this point, but he does have a Minor League option remaining. If the club opens the season with Romero on the 25-man roster, they could lose both Lee and Montero, so the safe bet might be to see what Lee can do while Romero waits in the wings in Tacoma.

Romero's tough stop

SEA@LAA: Romero snares grounder to escape jam

3/15/16: Stefen Romero ranges to his left and grabs a grounder off the bat of Daniel Nava, then steps on first to end the inning

Veteran left-handed hitting Efren Navarro also figures to be sent to Tacoma, where he's an able fill-in for Lind if needed.

Utility infielderLuis Sardinas, a 22-year-old acquired by trade from the Brewers, seems to be the clear favorite. Servais has history with Sardinas from his days as a top Rangers prospect and the youngster has played extremely well this spring. His bat has been the biggest question coming up, but the switch-hitter has been red hot all camp and plays a strong shortstop as well as second and third, while even getting some center field work recently.

Sardinas' grand slam

OAK@SEA: Sardinas hits a grand slam to left field

3/23/16: Luis Sardinas hits a grand slam to left field and the Mariners take an 11-9 lead in the 5th inning

Chris Taylor and Shawn O'Malley are also in the mix, but Taylor hasn't hit well this spring. O'Malley had an excellent month as a September callup last year and has matched Sardinas offensively this camp, but Servais says the first priority for this utility situation is the ability to play shortstop and he feels Sardinas and Taylor have the edge there, defensively.

Bullpen
The most unsettled area on the club appears to be a relief crew that has seen injury issues sideline right-handers Evan Scribner, Ryan Cook and Justin De Fratus, as well as lefty Charlie Furbush. That's created opportunities for non-roster invitees Joel Peralta, Donn Roach and Blake Parker. Peralta, 40, seems like a lock to earn one of the five right-handed spots along with Steve Cishek, Joaquin Benoit and Tony Zych. The last spot currently boils down to Roach, Parker or returnee Mayckol Guaipe, with Roach pitching extremely well all camp and Parker making a solid case also after missing last year following elbow surgery with the Cubs.

Peralta picks off Ahmed

ARI@SEA: Joel Peralta picks off Nick Ahmed at second

3/19/16: Joel Peralta picks off Nick Ahmed at second base to end the frame

Starter Mike Montgomery's conversion to a lefty relief role could solve two issues as he is out of options, so that creates an opening for him and keeps him in the organization as starting depth if needed. Vidal Nuno fills the other southpaw slot with Furbush sidelined indefinitely.

But the bullpen also seems the most likely place for Dipoto to make either late trade or waiver wire additions, so stay tuned.